In general, an air conditioner comprises a heating apparatus, a cooling apparatus, a heat pump, an air cleaner, and etc.
The air conditioner is an apparatus that cools or heats an indoor space by performing a process of compressing, condensing, expanding and evaporating a refrigerant. Air conditioners may be classified as a general air conditioner in which a single indoor unit is connected to an outdoor unit or as a multi-air conditioner in which a plurality of indoor units are connected to an outdoor unit. The air conditioner includes a compressor, a condenser, an expanding valve and an evaporator. A refrigerant discharged from the compressor is condensed in the condenser and then expanded in the expanding valve. The expanded refrigerant is evaporated in the evaporator and then sucked back into the compressor.
In the case of an air conditioner capable of performing cooling and heating operations, when the air conditioner is in the cooling operation, an outdoor heat exchanger serves as a condenser that condenses a high-temperature and high-pressure refrigerant discharged from a compressor into a liquefied refrigerant by performing a heat exchange. An indoor heat exchanger here serves as an evaporator. When the air conditioner is in the heating operation, the outdoor heat exchanger serves as an evaporator that evaporates a refrigerant, which may be in a mixture state of gas and liquid collected from the indoor heat exchanger, into a gaseous state by performing a heat exchange. The indoor heat exchanger here serves as a condenser.
In the conventional air conditioner, when outdoor temperature rapidly falls down due to a cold wave or where low-temperature heating is performed in a cool region, evaporation pressure falls down, the suction density of the compressor is decreased, and it is difficult to obtain a mass flow rate necessary for the heating operation. Therefore, heating performance may be considerably deteriorated. In a case where the air conditioner is replaced by a large-capacity air conditioner or a new air conditioner is additionally provided, cost of installation is increased, and a space for installation needs to be secured.